Gastrointestinal: USMLE Step 1 video lessons
Digestion, absorption, hepatobiliary physiology and gastrointestinal disease.
The gastrointestinal hormones, gastric acid secretion and the drugs that block it, H. pylori and peptic ulcer disease, and bilirubin metabolism and the causes of jaundice.
5:14GI hormones: gastrin, CCK, secretin, GIP and motilin
Each gut hormone answers one question: what has just arrived, and what must the gut do about it? Match every hormone to its source cell, its stimulus and its actions.
4:52Gastric acid secretion: the parietal cell, step by step
Three signals converge on one proton pump, and acid also brakes its own release. Follow the parietal cell, then see where PPIs, H₂ blockers and somatostatin act.
5:14H. pylori and peptic ulcer disease: how mucosal defence fails
More than a third of people worldwide carry H. pylori, yet only a minority develop an ulcer. This lesson builds the balance between acid and mucosal defence, then shows how H. pylori and NSAIDs break it.
5:44Bilirubin metabolism and jaundice: pre-hepatic, hepatic, post-hepatic
Jaundice is one sign with three places to fail. Follow bilirubin from haem to the gut, then use the fraction, the enzymes, the urine and the stool to find where the pathway breaks.